Fluid power cylinders are well known in the prior art. Such cylinders typically include a body which encloses an elongated cylindrical chamber. A piston is housed within the chamber. The piston is moveable longitudinally in the chamber in response to fluid pressure which is selectively applied to the areas on the sides of the piston. A piston rod is attached to the piston and extends through an opening in the body. The piston rod is attached to a mechanism that is to be selectively moved.
Pneumatic fluid power cylinders operate through the selective application of compressed air to the areas on the sides of the piston. In pneumatic cylinders, resilient seals are typically provided, both on the piston and adjacent the opening through the body through which the piston rod extends. The seals on the piston prevent the escape of air pressure from one side of the piston to the other. The seal adjacent the opening through which the piston rod extends prevents the escape of air pressure from inside the cylinder to atmosphere.
The seals on the piston and the piston rod are dynamic seals that extend between surfaces that are relatively moveable. These seals may wear as the result of repeated cycling of the cylinder. Wear may be reduced by providing lubrication to the seals.
In the past, lubrication has been provided by applying grease or other lubricant to the seals and the other components when the cylinder is first assembled. While this is effective, after many cycles, the lubricant is worn off. Another approach has been to inject droplets of lubricant into the compressed air supplied to the cylinder. This is effective but is becoming less desirable because of the possible release of the lubricant to the environment. It is also inconvenient to maintain the apparatus that injects the lubricant and to keep it filled with lubricant.
Another approach to lubricating piston seals of a pneumatic cylinder has been developed by Lehigh Fluid Power, Inc. of Easton, Pennsylvania. This approach involves providing a reservoir for lubricant within the interior of the piston and using a wick to move the lubricant out of the reservoir and onto the inner wall of the chamber in which the piston is housed. The lubricant moves from the reservoir to the wall of the cylinder on the wick by capillary action. Lubricant applied to the inside wall of the chamber is transferred to the seals through movement of the piston.
The problem with this approach is that it requires the use of a specially designed piston which includes an internal reservoir and a wick. It also does not provide lubrication for the rod seal.
Another approach that has been taken by Peninsular, Inc. of Roseville, Michigan, and Hennells, Inc. of Ferndale, Michigan to extend seal life, has been to provide a lubricant reservoir both in the piston and adjacent the rod seal. Peninsular uses a wiping pad over the opening to the reservoirs to draw the lubricant out and slowly apply it onto an adjacent moving surface. Hennells slowly passes its lubricant out of the reservoirs through a ring with a series of small holes. The drawback associated with these approaches is that the cylinder housings and pistons must be specifically made to accommodate the reservoirs and the structures for depositing the lubricant on the moving surfaces. The inclusion of these added features may make the parts larger and may add cost to the products.
There is a very large population of pneumatic cylinders currently in use that do not include provisions for internal lubrication of the piston rod and piston seals. These pneumatic cylinders cannot be readily adapted to include such systems. Such pneumatic cylinders would benefit from an apparatus for self lubricating the seals as this would extend seal life and reduce the need for external lubrication.
Thus there exists a need for a system that provides lubrication to piston and rod seals in cylinders that do not have built in structures for internal lubrication. There further exists a need to provide lubrication for piston and rod seals to extend seal life.